PLC Cross-Reference Guide: Siemens S7-1200 vs Delta AS300 vs Inovance H3u

Why this comparison exists

Every automation engineer in Southeast Asia eventually faces the same decision: stick with the brand you know, or evaluate a cost-effective alternative. This guide is not about which PLC is "best" — it is about which one fits your application, your budget, and your timeline.

We compare three platforms popular in the region today:

• Siemens S7-1200 (1200-series, current generation) — the industry standard
• Delta AS300 (Taiwan) — a fast-growing mid-range alternative
• Inovance H3u (China) — cost-effective and widely adopted in Vietnam/Indonesia

Hardware at a glance

Siemens S7-1200

• CPU options: 1211C through 1217C, plus fail-safe (F) variants
• Onboard I/O: Up to 14 DI / 10 DO / 2 AI on the 1215C; expansion via signal boards and modules
• Communication: PROFINET (built-in), with optional RS485/RS232 signal boards. PROFINET is the killer feature — deterministic, fast, and deeply integrated with Siemens drives and HMIs.
• Memory: Work memory 50–150 KB depending on model; load memory 1–4 MB
• Build quality: Injection-molded housing, IP20, industrial temperature range. Feels like what it costs.

Delta AS300

• CPU options: AS332T, AS324MT, AS316T, and compact AS218RX
• Onboard I/O: Comparable to S7-1200 mid-range — AS332T has 16 DI / 12 DO with transistor outputs at 0.5A per point
• Communication: Ethernet, RS485 (built-in Modbus RTU), CANopen. Supports EtherNet/IP and Modbus TCP. No native PROFINET — if you need Siemens drive integration, this is not your PLC.
• Memory: 128 KB program, 64 KB data — generous for the price point
• Build quality: Good. Compact DIN-rail design, removable terminal blocks. Not quite Siemens-level fit and finish, but closer than you would expect at the price.

Inovance H3u

• CPU options: H3u-1616MT, H3u-3232MT, H3u-3624MT etc. The numbering convention is straightforward: first two digits = DI count, second two = DO count.
• Onboard I/O: Up to 36 DI / 24 DO on larger models — on-paper I/O density is higher than comparable S7-1200 models
• Communication: Ethernet, RS485, CAN. Supports Modbus TCP/RTU. No PROFINET. Motion control via CANopen.
• Memory: 256 KB program (larger than Delta and mid-range S7-1200)
• Build quality: Functional. The plastic housing is noticeably lighter — not "cheap", but weight is a tell. DIN-rail mount. Removable terminals on most models.

Programming: the real differentiator

Siemens TIA Portal

TIA Portal is an engineering framework, not just a PLC programming tool. You program the PLC, configure the HMI, set up drives, and commission safety — in one project. LAD, FBD, SCL, STL, and Graph are all supported. Libraries and reusable blocks are first-class citizens.

The cost: TIA Portal licenses are not cheap, and the learning curve is steep for engineers coming from simpler platforms. If your team already knows TIA Portal, this is a huge asset. If they do not, budget for training.

Delta ISPSoft / DIADesigner

Delta's programming environment has improved significantly. ISPSoft supports Ladder, SFC, and structured text. DIADesigner adds motion control configuration. The interface feels like it was designed by engineers (functional, a bit clunky, but it works).

One advantage: Delta's documentation is available in English, Chinese, Vietnamese, and Thai — reflecting their strong SEA distribution. If your maintenance team reads Thai or Vietnamese, this matters.

Inovance AutoShop

AutoShop is Inovance's programming software. Ladder and structured text. The UI is clearly inspired by Japanese PLC programming tools (Mitsubishi GX Works heritage is visible). Functional but not polished. English documentation exists but is less comprehensive than Delta's.

The good news: it is free. No license fees, no activation headaches. For small shops that cannot justify a TIA Portal license, this is a real factor.

Lead times and availability in SEA

This is the practical factor that tips many decisions:

If your project timeline is tight, Siemens from authorized channels is a risk. The workaround — Chinese-market S7-1200 stock from Shenzhen — is genuine Siemens hardware, but verify firmware compatibility with your TIA Portal version.

Delta and Inovance stock is generally plentiful across Bangkok, Ho Chi Minh City, and Jakarta distributors. This is one reason they are gaining share in SEA.

Cost comparison (ballpark, 2026)

Approximate pricing for a comparable mid-range CPU (16+ DI, 12+ DO, Ethernet):

• Siemens S7-1214C DC/DC/DC: ~USD 350–480 from authorized, ~USD 280–380 from Shenzhen channels
• Delta AS332T: ~USD 150–220
• Inovance H3u-1616MT: ~USD 100–160

For a line with 20 stations, the difference between Siemens and Inovance is USD 5,000–7,000 on CPU cost alone. Add I/O expansion and HMI, and the gap widens.

When to choose which

Choose Siemens S7-1200 when:

• Safety (fail-safe CPUs, PROFIsafe) is required
• You need PROFINET integration with Siemens drives and HMIs
• The customer specification or end-user preference mandates Siemens
• Your team is already TIA Portal-competent
• Long-term spare parts availability is critical (Siemens supports products for 10+ years after discontinuation)

Choose Delta AS300 when:

• Budget is tight but you need solid reliability and good documentation
• Your factory is in Thailand, Malaysia, or Vietnam (Delta has strong local support)
• Modbus TCP is sufficient for your communication needs
• You are replacing a legacy system and want a modern PLC without paying Siemens prices

Choose Inovance H3u when:

• The application is non-safety-critical and straightforward
• Lead time is the #1 priority (Shenzhen stock ships same-week)
• You are building machines for export where cost per unit matters
• Your team can work with AutoShop's functional-but-not-polished software

The honest bottom line

Siemens S7-1200 is the reference standard for a reason — TIA Portal, PROFINET, and the ecosystem are genuinely better. But "better" costs money and time, and not every application needs better. A Delta AS300 running a conveyor line in Bangkok performs the same task as an S7-1200 at half the cost and a fraction of the lead time. An Inovance H3u in a Vietnamese packaging machine ships tomorrow while your Siemens rep says Q4.

The right question is not "which PLC is best" — it is "which PLC keeps my production running at an acceptable cost." For many SEA factories in 2026, the answer is not always the one with the blue logo.